1. Field of the Invention
The present invention relates to a method for processing a semiconductor device, and more particularly to a method for self-trimming patterns (e.g., looped patterns) formed by techniques such as using sidewall spacers, sidewall image transfer, or phase edge image transfer via a phase shift mask (e.g., normally requiring a trim mask to separate the resulting pattern) without using a trim mask.
2. Description of the Related Art
Processing of semiconductor devices typically involves formation of patterns (e.g., looped patterns) formed by techniques such as using sidewall spacers, sidewall image transfer, or phase edge image transfer via a phase shift mask. To separate such looped patterns, typically a trim mask is used to separate the pattern (e.g., see FIG. 2).
However, the trim process is an extra lithographic step which involves a photo mask and related process steps, such as resist coating, exposure, developing, and stripping, etc. The trim process results not only in higher cost, but also a higher probability of contamination. Thus, while the looped patterns are useful, especially since they can result in a sub-lithographic pattern which separately could enhance the device packing density without relying on expensive lithographic techniques, the looped pattern requires the trim mask.
Therefore, using such looped patterns without requiring a trim mask would be helpful in the semiconductor industry. Hitherto the present invention, such has not been accomplished.
It is noted that an existing process which performs trimming and avoids using a mask is described in copending U.S. patent application Ser. No. 09/224,768, to Arndt, et al., having IBM Docket No. FI9-98-147, filed on Jan. 4, 1999 entitled xe2x80x9cMETHOD OF PRODUCING SELF-TRIMMING SUBLITHOGRAPHIC ELECTRICAL WIRINGxe2x80x9d.
In the copending application, a recess in a deposited layer is created such that selected sides of the recess have sloped sidewalls and the remaining sides of the recess have vertical sidewalls. A phase-shifted region of the mask used to define the recess produces the sloped sidewalls, while the vertical sidewalls result from the non-phase shifted portion of the mask. Sidewall spacers form only on the steep sidewalls of the structure.
Hence, no looped pattern will be formed, and there is no need for trimming. However, this method requires an expensive mixed phase mask. Furthermore, since shallow slopes are involved in the pattern layout, the packing density is limited.
Thus, prior to the present invention, there has been no method which avoids the use of a separate trim mask to define the portion of a looped pattern to be trimmed. Thus, the conventional techniques have been costly and inefficient.
In view of the foregoing and other problems, disadvantages, and drawbacks of the conventional methods and structures, an object of the present invention is to provide a method in which looped patterns are processed without requiring a trim mask.
Another object is to provide a method for performning a maskiess, or self-trimming processing of such looped patterns, so that they can be useful for different applications, such as forming conductors, resistors, fuses, etc.
In a first aspect of the present invention, a method of self-trimming a pattern includes forming a pattern containing a plurality of regular or irregular densely packed features using a first material deposited on a substrate, forming sidewall spacers using a second material along the sidewalls of the pattern in the first material, depositing and etching back a third material, such that the third material covers a portion of the sidewall spacers, and etching to remove the uncovered portion of the sidewall spacers.
In a second aspect of the present invention, a method of self-trimming a pattern includes forming a pattern within a first material deposited on a substrate, depositing a conformal layer of a second material, and etching the second material to form spacers of a second material along the sidewalls of predetermined patterns in the first material.
Preferably, the method further includes depositing a third material to fill spaces of the pattern in the first deposited material, and etching back the third deposited fill material to expose the patterns at exterior boundaries, the etching back partially removing the third deposited material from between adjacent lines of the first material, and the method further including removing the exposed patterns via an etching, and stripping the remaining third deposited fill material.
With the unique and unobvious aspects of the invention, patterns (e.g., looped patterns) can be used without requiring a trim mask. Further, no expensive phase-shift mask is required, as in the copending U.S. patent application Ser. No. 09/224,768. Additionally, the invention provides a high packing density. Thus, in the invention, a method is provided which avoids the use of a separate trim mask to define the portion of the looped pattern to be trimmed. Hence, the invention offers significant cost savings over the existing techniques.
Further, besides trimming the looped pattern, the method is flexible, and can trim other kinds of patterns depending on the layout design. These other patterns include, for example, a fish-bone shape, a comb shape, etc.